Method and apparatus for inscribing a pattern in a target electrode structure



April 10, 1956 W O- REED METHOD AND APPARATUS FOR INSCRIBING A PATTERN IN A TARGET ELECTRODE STRUCTURE Filed Sept. 27, 1950 u F/'gl E@ @MOSES WILLIAM O. REED INVENTOR United tates arent o ice METHOD AND APPARATUS FR INSCRIBING A `PATTERN lN A TARGET ELECTRODE STRUC- TURE William 0. Reed, Chicago, lll., assigner to The Ranland Corporation, a corporation of Illinois Application September 27, 1950, Serial No. 187,123 7 Claims. (Cl. 315-12) This invention relates to a novel method of inscribing a pattern in a sheet of material. Although it is subject to numerous applications, the invention is ideally suited for producing a storage electrode for a signal storage device of the type described and claimed in the copending application of Constantin S. Szegho and William O. Reed, filed June 16, 1949, Serial No. 99,421, now Patent No. 2,687,492, and assigned to the same assignee as the present application. For convenience, the invention will be described in that connection.

structure, or in other words, the most numerous the interstices the greater the resolution. A mesh having 400 vopenings per square inch has been found suitable for many applications.

A member provided with a plurality of interstices to serve as' a storage electrode, such as the one just described, may be formed by conventionally weaving a screen of conductive wires. Alternatively, the electrode may be fabricated by perforating a conductive sheet to produce the required pattern of apertures. In order to achieve a suitable number of apertures per unit area, complex and expensive mechanical fabricating devices are needed. Since these fabricating devices are but machines, there exists a practical limit to the fineness of screen which vcan be easily attained, and consequently, the image resolution of the signal storage device is limited.

A ,'Conductive meshes having a large number of interstices may also be formed by well-known electrolytic and chemical means. However, there is a practical limit of open area in comparison to mesh bar area for structures fabricated in this manner.

It is an object of this invention, therefore, to provide j a novel method of inscribing a pattern in a sheet of material which method is not subject to the limitations of prior processes.

It is a further object of this invention tol provide a novel method of inscn'bing a pattern in a sheet of material which is efficient in execution and yet is inexpensive to carry out.

An important feature of the invention is a method of inscribing a pattern in a target electrode structure ,which has `a given secondary emission characteristic. AThe method comprises the formation of a beam of electrically charged particles which is directed toward a particular elemental area of the electrode structure materially to alter the secondary emission characteristic of` that area. The beam is deflected in response to a pre-" :ent invention.

.layer shouldl be thin enough so that it may different secondary 'plication This device is of the double ended selected change of secondary emission characteristic in step-by-step fashion over the electrode structure in accordancewith a preselected pattern similarly to alter the secondary emission characteristic of the scanned area of the electrode structure. A preferred embodiment of this feature utilizes a beam of electrons as the agency for inscribing the pattern, which is formed by melting apertures in the electrode structure.

Another feature of the invention provides a novel apparatus for inscribing a pattern in a target electrode structure having a given secondary emission characteristie. The `apparatus comprises means for developing a beam of electrically charged particles and a deflection system is associated with the beam to direct the particles toward a particular elemental area of the electrode structure. The deflection system is responsive to a control potential for displacing the beam to another elemental area of the electrode structure. A load impedance is connected in the circuit with the beam-developing means for deriving a control potential when the secondary emission characteristic of the lirst elemental area is altered a selected amount. The apparatus further includes means for coupling the load impedance to the deection system to effect displacement of the beam from the rst area to another elemental area of the electrode structure in response to the control potential.

The features of the present invention which are believed to be novel are set forth with particularity in the .appended claims.` The present invention, both as to its organization and manner of operation, together with further objects and advantages thereof may best be understood by reference to the following description taken in connection with the accompanying drawing in which:

Fig. 1 is a block diagram of apparatus for inscribing a pattern in a sheet of material in accordance with the method of the instant invention and includes a sectional view partly schematic of a signal storage device which constitutes a part of this apparatus;

Fig. 2 is a fragmentary view of a storage electrode fabricated by the method of the instant invention;

Fig. 3 is a sectional view taken along line 3 3 of Fig. 2.

With reference now to Fig. l, there is shown an apparatus especially suited for inscribing a pattern in a sheet of material in accordance with the method of the pres- This apparatus comprises an electrondischarge device itl-having an evacuated glass envelope 11 which encloses a sheet of conductive material 12 disposed on a support structure 13 of an electrical insulating material. The structure 13 may for example be a rectangular plate of quartz, glass, mica or similar material land sheet 12 may be a layer of silver, copper, or like material coated on one face of the plate. The metal be locally heated and melted. The material of sheet 12 normally has a given secondary emission characteristic and when the sheet is processed by the method of the invention it is inscribed with a pattern of areas having a materially emission characteristic. Specifically, a permanent pattern of apertures is produced in the Ametallic layer and the structure 12, 13 becomes a storage electrode for device l0, as will be more-fully described hereinafter.

Except for the construction of target electrode 12, 13, the device 10 is generally similar to the signal-storage device described in the aforementioned Szegho-Reed apvariety and the portions thereof to the right and to the left of "structure 12, 13 are identical. With reference only to the right-hand portion of device 10, the evacuated envelope 11 encloses an electron gun 14 which constitutes the means for developing a beam of electrically charged paricles, namely electrons. The electron gun includes a first .node 15, a control electrode 16J a cathode 17 .and .a leater filament 18 for maintaining cathode 17 at a suit- Lble operating temperature. The device also includes tn accelerating electrode 19 followed by 1a decelerating electrode 2G. ln practicing the invention to process Vtar- ;et electrode `1.2, 13, the normal role of electrode 20-as a ecelerator is not employed and this Velectrode Vis coniected externally of envelope 11 with accelerating elecrode 19 both of which are grounded. A source o'f unilirectional potential 21`is connected 'between electrodes l5 and 19 to produce the required potential difference :herebetween and a source of unidirectional accelerating potential 22 is connected between electrode 15 and cathode 17. Control electrode 16 is connected to one end of an isolation resistor 23, the other end of vwhich fis'connected to the wiper arm of a potentiometer 124 shunted across a source of bias potential 25. The positive terminal of source 25 is connected to cathode 17 land the-negative terminal is connected to control electrode 16 through a pair of normally open contacts 26 of a relay 27. A sourceof filament potential '25a is connected to iilament `18.

A load impedance 28 is connecte'dbetween the conductive target sheet 12 and ground and hence is '1in circuit with lthe beam-developing means which includes electron gun 14. This load impedance is effective for deriving a control pulse when the secondary emission 4characteristic of a portion ofthe sheet 12 is altered agpreselected amount, or in other words when 'the electron lbeam'locally heats an elemental area of sheet' 12 Von which Ait impinges to cause melting and so form an aperture therein a voltage pulse V'is 'derived across load 28. 'The load impedance is also eliective for deriving a dierent type `of pulse when thefelectron beam is deected olf sheet 12. In particular, the tiret-mentioned pulse is characterized by va leading edge having a rise time dependent upon the rate 'at which the material of the treated area is melted vand 'this rise time is slow compared with that of the last-mentioned variety of pulse.

Load impedance 28 is coupled with a pulse-separator 29 which is e'ective to separate pulses of different 'rise times and may be of 'any well-known construction. 'The stage 29 has one pair of output terminals 29a across which voltage pulses having a slow rise time appear and vanother pair of output terminals 29h across rwhich vvoltage pulses having a faster rise time appear. Terminals 29a are coupled to a rst single-shot multivibrator 30, -which may be of conventional form, arranged to iire once to produce a pulse of given voltage amplitude for every pulse applied to its input circuit. The output circuit of v multivibrator 30 is coupled with a voltage integrator '31 Ywhich integrates the magnitudes of successive `voltage pulses developed by stage 3i). This integrator'maycomprise a capacitor and an associated circuit 'for operating the capacitor over the linear lportion of its charge-time .f

characteristic in known manner. The 'output terminals of integrator 31 vare vconnected with a conventional direct-'coupled amplifier 32 through an amplitude control 33 and the output circuit of the amplilier is coupled'with the horizontal deection coils 34 of device 10. A source of B-potential 35 supplies space current for stage 32 and a positioning control 35 is coupled to a source of positioning voltage 37 :and to coils 34 to provide means v'for adjusting the quiescent position of the beam from gun 14 in a horizontal direction. A discharge .device B8 is coupled with integrator 31 to discharge the .capacitor thereof in response to a signal supplied to its input circuit Which is coupled to terminals 29b of pulse separator 29.

The terminals ,2911 of pulse separator .29 are further coupled with a multivibrator 39 of another .channel similar to the one just described and which likewise includes .a voltage integrator 40, a direct-coupled amplier 4l and an amplitude control 42. Stage 41 derives .its B-power from supply source 35 .and its output circuitisconnected to Avertical deflection coils 43 which are coupled with a vertical-positioning control 44, in turn, connected .to source 37. A discharge device 45 is coupled with integrator 40 and its input' circuit is shunt'ed by a normally open discharge switch 46.

The coils 34 are a part of a deflection system associated with the beam of electrically ycharged particles emanating from gun 14 for directing the particles toward an-elemental .area of sheet '12. The deflection -system is responsive to a control potential for displacing the beam `from one to another elemental area of the sheet. Stage 32 provides the means for coupling integrator '31 toco'il B4 of the deect'i'on system to effect lsuccessive displacement of the beam across a succession yof y.elemental :areas of sheet 12 in response to the control potential developed by integrator 31. The pulse separator 29 which effectively is coupled between the load impedance 28 and integrator 31 through discharge device 38, selectively re- Lturns the integrator to fa discharged or quiescent condi- `tion only in response to the .type ofpulse that is 'derived whenthe electron beam is deected Loff the sheet.

'Tube 10 is provided with a conventional focusing coil '-47 and a suitable current source 48 is coupled thereto Ythrough a focus control 49. The current from vthis source is adjusted by means of control 49 so 'that 'the 'beam of .electrons from gun 14 is directed in va focused `spot toward vtarget 'sheet 12.

In addition to being coupled with lseparator 29, lload impedance L28 is coupled to a discharge device 50,'in1turn, coupled vwith 'a third voltage integrator 51. This fintegrator whichis similarto integrator 31 includes :one-set 'of terminals coupled with a source of ixed potential 52 Vand vits .output terminals are coupled with the actuating `'coil 53 of'relay 27.

lThe relay '27 is provided with a second 4set of conitacts 54. These contacts are normally open and are in -'circuit with an indicator system including a source .of potential 55 'and `an vindicator lamp S6.

In describing the operation of the apparatus of Fig. l, Ilet it -be assumed that integrators 31, 40 and 51 rare :in their respective vquiescent or discharged conditions. The currents in the deflection system :including coils 34 and 43 are adjusted by means of controls .36 and 44 so `that Lthe beam of electrons from gun 14 strikes the sheet 12 at :its upper left-hand corner, looking at the sheetfrom v.the -gun -end `of device 10. Electrons that strike the conductive sheet' lfind a Areturn ,path to ground through :load 28 fand "locally heat the `sheet in the area ,on which they lstrike. A suicient accelerating potential is .provided vby :source 222 and a lsuitable rbias .is provided for grid`16 so -thatthe lheating of the sheet produces melting anda substantially 'circular aperture is formed in thersheet.

`When this occurs, 'some lof the electrons pass through -the newly formed openingand the current flowing `.through load 28 changes to effect a'voltage pulse across-,the load. This typeofipulse is of the type having va relatively slow risetime'and is not translated to-multivibrator39 byfdis- -crirninator 329, but is supplied `to multivibrator'30. The vresulting pulse lfrom multivibrator '-30 is stored in tintegrator 31 and the voltage increase of the Vintegrator gis-supplied as a currentchange to the horizontal deecti'onscoil 34 through ltranslator 3 Thus, the 'electron beam '-is deflected in a horizontal direction by a predetermined amount and is directed to another elemental area ofthe `sheet adjacent the initially treated area. Separator 29 is etective to preventthe transfer of a -pulse to y.either of the multivibrators '-30 or 39 in response lto the rvoltage change across load 28 eiected by movement -of the `beam "from the area ot the newly formed aperture Vto the :body 'of the yconductive sheet.

aperture is now formed .in the elemental area .of :the sheet .adjacent .the .hist-mentioned .aperture in the .mannerdescribed .and a second voltage pulse is -ier'ived .across .load 28 whenithe opening `is etected. This pulse triggersmultivibrator 30 yagain and .another voltage pulse of constant amplitude is, supplied to integrator 31 which is added to the voltage already stored therein. The current in deection coil 34 is changed by another preselected incremental amount and the beam is shifted to another elemental area of the sheet 12. This process continues until the beam has scanned the sheet to form a line of apertures across the upper extremity thereof.

When the beam is deflected olf the sheet a voltage pulse is derived in load 28 having a faster rise time than the pulse formed in response to aperture production. This steeper pulse tires only multivibrator 39 and a voltage pulse of constant amplitude is applied to integrator 40. The increase in voltage in integrator 40 effects a current change in vertical deflection coil 43 through amplifier 41 and the beam of electrons from gun 14 is displaced in a downward direction by a preselected amount. At the same time, the pulse from separator 29 that effects vertical beam movement operates discharge device 33. The operation of device 38 discharges integrator 31 which returns to its quiescent condition and the beam of electrons is carried to the left-hand boundary of sheet 12. The aforedescribed sequence for the first line of sheet v12 is repeated and a second line of apertures in vertical alignment with the first line is produced.

The sequence of line scanning continues until the beam has scanned the entirety of sheet 12. After the beam is dellected beyond the lower right hand extremity of the sheet, it is returned toward the left-hand boundary at the same time it is displaced downwardly. This places the beam below the lower left-hand extremity of sheet 12. In this operating condition no aperture formation occurs and the afore-described sequence of aperture-forming operations thus ends. If it is desired to repeat the sequence, switch 46 is closed whereupon discharge device 45 returns integrator 40 to its cycle begins again.

During the aperture-forming operations, integrator 51 tends to accumulate a voltage charge from source 52.

quiescent condition and the However, the pulses from load 28 continually cause. dissipa'tion of this charge through the operation of discharge device 50. A charge does build up within integrator 51 when the electron beam is disposed beyond the contines of the lower left-hand corner of sheet 12 since for this condition no sequence of pulses appears across load 28 and a sufhcient voltage is produced to energize coil 53 of relay 27. The resulting magnetic eld of coil 53 closes `contact 26 to turn oi the beam of device 10. This field also closes the indicator lamp circuit through contacts 54 and indicator lamp 56 aords a visualindication that the entire aperture-forming sequence has been completed.

.The just-described system for detlecting the electron beam .in response to a pre-selected change of secondary emission characteristic of the target is provided with means sensitive to the rise time of the pulses developed in the target load impedance for designating horizontal i and vertical scanning steps, respectively. It is entirely within the scope of the invention to utilize .the different pulse amplitudes produced by aperture formation and by deflection of the beam off the target for designating scanning steps. This may be achieved by employing any well known circuit construction in stage 29 that is effective for separating pulses of different amplitudes and operating the remainder of the system essentially as described hereinbefore.

With reference now to Fig. 2, the plan view there represented shows the sheet 12 after a pattern of apertures has been formed in accordance with the above-described sequence of operation for the apparatus of Fig. 1. These apertures are circular in shape and their diameter may be predetermined by the beam intensity from electron gun 14 and/or the time interval that elapses between the rst appearance of a small aperture in the elemental area being treated and the deection of the electron beam from that area. This time interval may be preset by providing a suitable time delay adjustment in separator 29 or in multivibrator 30. As better illustrated in Fig. 3, the material that is removed to form the aperture tends to build up the area of the sheet surrounding the apertures into a crater-like coniiguration. However, for practical purposes when utilized in device 10, the insulator 13 is substantially coplanar with sheet 12 and the structure 12, 13 may be properly operated as a storage electrode. It is mjportant to note that as soon as the aperture-forming operations are completed, nothing further need be done before device 10 is connected into another circuit for operation as an image storage device, for example, in the circuit of the afore-mentioned Szegho-Reed application.

From the above discussion it is apparent that theap'- paratus of Fig. 1 is effective for inscribing a pattern in a sheet of material having a given secondary emission char'- acteristic. This method comprises, as a rst step, the formation of a beam of electrically charged particles such as electrons. The beam is directed toward an elemental area of the sheet to be inscribed, materially to alter the secondary emission characteristic of this area. Specifically, the area toward which the beam is directed is melted to form an aperture, and hence the secondary emission characteristic is changed from some given value tozero, assuming for this discussion that the insulator 13 does not contribute to the secondary emission characteristic of sheet 12. If the composite target be considered, the secondary emission. is low for the conductive surface and a large number of electrons flow at the outset. After an aperture is formed to expose the insulator target portion, the electron beam charges the insulator and electron ow to the conductive target portion is greatly altered. The beam is then deflected over the sheetuin accordance with a preselected pattern determined ,by the integratoramplifier systems as described above similarly to melt other elemental portions of the scanned area of the sheet.

It is apparent that by suitably adjusting the accelerating potential which causes electrons to strike sheet 13 to form small apertures and by closely spacing the series of apertures relative to one another, a much finer mesh may be constructed than heretofore possible by mechanical methods. No intricate mechanical device is needed to carry out the method of the invention and, in general, the relatively simple electronic apparatus for carrying it out `is less complex and less expensive that the mechanical fabricating devices employed in practicing the prior-art methods.

While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that, changes4 and modifications may be made without departing from this invention in its broader aspects, and, therefore, the aim in the appended claims is' to cover all such changes and modifications as fall within the true spirit and scope of this invention.

I claim:

1. The method of inscribing a pattern in a target electrode structure having a given secondary emission characteristic which comprises the steps of: forming a beam of electrically charged particles; directing said beam toward an elemental area of said electrode structure materiallyv to alter the secondary emission characteristic of said area; and deecting said beam in response to a preselected change of secondary emission characteristic in step-by-step fashion over said electrode structure in accordance with a preselected pattern similarly to alter the secondary emission characteristic of other elemental areas of said electrode structure.

2. The method of inscribing a pattern in a target electrode structure having a given s'econdary emission characteristic which comprises the steps of: forming a beam of electrically charged particles; directing said beam toward an elemental area of said electrode structure materially to alter the secondary emission characteristic of said area; delecting said beam in response to a preselected change of secondary emission characteristic in step-bystep fashion over said electrode structure in accordance 7 witha ,preselectedpattern similarly to alter the secondary emission characteristic 'of other elemental areas of said electrode structure; and 4interrupting the Adeflection o said beam when 'said lbeam has completed a `selected number ofscansions of said electrode structure.

3. The metho'd of inscribing a pattern in a 'target electrode structure having a given secondary emission 'characteristic'whic'h comprises the steps of: 'forming a beamof electrons; directing said beam toward an elemental area of Said .electrode structure materially to alter the secondary .emission characteristic of-said area; and deilecting said beam in response to a .preselected change of secondary emission characteristic v.in step-by-s'tep V'fashion over .said electrode .structure in accordance with a preselected Ypattern similarly to .alter .the secondary emission characteristie o'f thescanned area o'f said .electrodestru'cture- 4. The method ofinscribing .va pattern in a target electrode .structure .formedfrom a sheet of material having a ,given .secondary .emission characteristic which comprises thesteps of: forming a beam of electrically charged particles, directing said 'beam toward an elemental area of :said Velectrode structure to melt said material and alter .the secondary emission characteristic of said area byfformling an aperture in said target electrode structure generally corresponding to said area; and deflecting said beam in response to a preselected change of secondary emission .characteristic .in step-by-step fashion over said electrode .structure and in accordance with a preselected pattern similarly ,to melt said material and effect apertures in ,other portions of the scanned area of vsaid electrode structure.

5. .Apparatus for inscribing a vpattern in a target elec- Atrade structure .having a given secondary emission charl.acteristic comprising: an envelope, a target electrode structure having a given .secondary emission characteristic mounted therein, means for developing a beam of electrically charged particles; a deflection .system associated with said beam for directingsaid particles toward an .elemental area of said electrode structure and responsive .to a control potential ffor displacing said beam to another elemental area of 'said electrode structure; a.load impedance in circuit with said beam developing means for derivling .a controlppotential when the secondary emission characteristic of said first-mentioned area is altered a preselected amount; .and means for coupling said load impedance to said deection system to effect displacement of said 4beam from said 4first-mentioned area .to another `elemental area of said electrode structure in response to 'said control potential.

6. Apparatus for inscribing a pattern in a target :elec- 'trode structure having agiven secondary emission charac- "terist'ic comprising: an envelope, a target electrode struc- `ture having a given 'secondary emission characteristic mounted therein, .means for developing a beam of electri- 'cally chargedjp'articles.; a dellec'tion system Yassociated with said beam for directing said particles .toward an elemental area of said .electrode'structure and responsive to a control potential 'for displacing Asaid beam to `another elemental area of said electrode structure; a load `rimpedance in .'circuitwith saidbeam 'developing means for deriving a vvoltage zpulse when the secondary emission characteristic of 'any elemental 'areaof 'said electrode structurels altered `a preselected amount; anintegrator coupled 'to said load`im pedancefor integratingisuccessive voltage pulses developed by said impedanceto .derive a controlpotential; and means for couplingfsaid integrator to said deection system .to electsuccessive displacement of said beam across asuccession of elemental areas of said electrode structure 1in "response to :said control potential.

'7. Apparatus 'for inscribin'g appattern in a target electrode structure having a given secondary emission characteristic comprising: an envelope, va targetelectrode structure having Ja given secondary emission characteristic mounted therein, means for developing a beam of elec- 'triclly charged particles; a deflection system associated 'with said vbeam for directingsaidpart'icles toward an elemental area of said .lectrode structure .and ,responsive `tn a control potential lfor displacing said beam to another telemental 'area of .said electrode structure; aload impedance 'in circuit with sa'id 'beam developing ,means for deriving `onetype of '.voltagepulse when said given secondaryem'ission characteristic of said elemental areais altered a given amount, and for deriving a different type of voltage pulse 'When said beam 'is deected olf said electrode structure; aninte'grator coupled to said'load impedance yfor integrating successive voltagejpu'lsesy of said tiret-.mentioned type to derive 'a control potential; means for coupling .said integrator tofsaid deflection system to effect successive .displacement of said beam across a succession of .elemental areas of said electrode structure in response tosaidcontrol potential; andapulse separator coupled .between saiddoad 40 jimp'edance and said integrator for selectively .returning integrator to a quiescent conditiononly .in Aresponse .to 'said different type of voltage pulse.

yReferencesCited inthe 'file of this patent' UNITED STATES PATENTS .2,034,704 Nakashima et al Mar. 24, 11936 .2,128,581 Gardner Aug. 3.0, 193:8 '2,130,134 'I'ams Sept. 213, 1938 '2,267,752 .Ruska et al `Dec. '30 1941 42,345,080 'Von Ardenne Mar. .28, 1944 2,434,930 Johnson Jan. 27, 1-948 2,434,931 `Johnson --.Ian .'27, 194B '2,495,042 'Wilderet al Ian. 17, .1950 

